Self-monitoring of blood glucose is a critical part of managing diabetes. However, present procedures for obtaining such information are invasive, painful and provide only periodic measurements. Standard methods of measuring involve the use of painful and cumbersome finger stick blood tests. Thus, development of a painless and automatic approach would represent a significant improvement in the quality of life for people with diabetes. Further, a tight glucose control regimen, which uses frequent glucose measurements to guide the administration of insulin or oral hypoglycemic agents, leads to a substantial decrease in the long-term complications of diabetes. See, Diabetes Control and Complication Trial Research Group (1993) N. Engl. J. Med. 329:997–1036.